如何简化这段代码以降低复杂度？

Question

由于有很多 if 语句，下面的代码非常复杂。如何简化这部分代码？把最新的else if改成无条件的else语句，代码会不会简化？它会以同样的方式起作用吗？parse(value: string): NgbDateStruct {  if (value) {    const date = value.trim().split('-');    if (date.length === 1 && isNumber(date[0])) {      return {        year: toInteger(date[0]),        month: undefined as any,        day: undefined as any      };    } else if (date.length === 2 && isNumber(date[0]) && isNumber(date[1])) {      return {        year: toInteger(date[1]),        month: toInteger(date[0]),        day: undefined as any      };    } else if (date.length === 3 && isNumber(date[0]) && isNumber(date[1]) && isNumber(date[2])) {      return {        year: toInteger(date[2]),        month: toInteger(date[1]),        day: toInteger(date[0])      };    }  }  return undefined as any;}

Answer 1

好吧，你的代码想起来很简单，但是很长！！

如果你想要示例，我有 javascript vanilla 代码：

function parse (value) {

    var list = (value + "").trim().split("-").reverse();

    if (list != 0 && list.every(x => !isNaN(x))) {

        return {

            year: parseInt(list[0]),

            month: parseInt(list[1]) || undefined,

            day: parseInt(list[2]) || undefined,

        }

    }

    return undefined;

}

// below for testing

[

    "08-11-2020",

    "11-2020",

    "2020",

    ""

].forEach(x => {console.log(x, parse(x))});

不幸的是，我没有任何实现打字稿代码的经验，但上面的 JavaScript 代码可能会对你有所帮助。实际上我缩短了代码，因为 javascript 带来的优点（缺点？），也许转换为 typescript 不会有太大区别！

附加打字稿代码：

在 typescriptlang.org 上

type NgbDateStruct = {

    year?: number;

    month?: number;

    day?: number;

};

function parse (value: string) : NgbDateStruct {

    var list = (value + "").trim().split("-").reverse().map(x => x || -1).map(Number);

    if (list.length > 0 && list.every(x => !isNaN(Number(x))) && list.every(x => x > -1)) {

        return {

            year: list[0] || undefined,

            month: list[1] || undefined,

            day: list[2] || undefined,

        }

    }

    return undefined as any;

}

// below for testing

[

    "08-11-2020",

    "11-2020",

    "2020",

    "",

    "nothing"

].forEach(x => {console.log(x, parse(x))});

Answer 2

一种选择是使用正则表达式来匹配数字，可能会散布-s：

const getDateObj = value => {

  const match = value.match(/(^\d+)(?:-(\d+)(?:-(\d+))?)?$/);

  if (!match) return undefined;

  const [, first, second, third] = match.filter(group => group !== undefined).map(Number);

  if (third) {

    // All were matched

    return {

      year: third,

      month: second,

      day: first

    };

  } else if (second) {

    // Only first two were matched

    return {

      year: second,

      month: first

    }

  }

  return {

    year: first

  }

};

console.log(getDateObj('31-12-2000'));

console.log(getDateObj('12-2000'));

console.log(getDateObj('2000'));

console.log(getDateObj('incorrect'));

在 TypeScript 语法中：

type NgbDateStruct = {

    year: number;

    month?: number;

    day?: number;

};

const getDateObj = (value: string): NgbDateStruct | undefined => {

    const match = value.match(/(^\d+)(?:-(\d+)(?:-(\d+))?)?$/);

    if (!match) return undefined;

    const [, first, second, third] = match.filter(group => group !== undefined).map(Number);

    if (third) {

        // All were matched

        return {

            year: third,

            month: second,

            day: first,

        };

    }

    if (second) {

        // Only first two were matched

        return {

            year: second,

            month: first,

        };

    }

    return {

        year: first,

    };

};